Manufacture of electrical coils



Aug. 8, 1967 A. R SMITH u MANUFACTURE OF ELECTRICAL COILS Filed Feb. 19, 1962 (l2 l9 l4 12. $11; 2 3; .f: f F g 28 22 -2e 26 IM" 27 as T W ADDISON ROMAINE SMITHJI ATTORNEYS United States Patent 3,334,413 MANUFACTURE OF ELECTRICAL COILS Addison Romaine Smith ll, Louisville, Ky., assignor to Anaconda Aluminum Company, a corporation of Montana Filed Feb. 19, 1962, Ser. No. 174,171 3 Claims. (Cl. 29-605) This invention relates to the manufacture of electrical coils. More particularly, it is directed to a method of forming electrical coils from rolls of conductor material having uninsulated side edges wherein the rolls are contacted along an edge portion of each turn during the anodizing operation. The invention also relates to an anodizing rack for anodizing the edges of the coils according to the method of the invention.

Electrical coils are often made up of a plurality of turns of flat aluminum strip with a continuous coating of dielectric material disposed between the turns of the coil to electrically insulate them from one another. Leaves of thin paper or a film of insulating enamel, varnish or lacquer, are ordinarily used as a dielectric coating between the turns of the strips. An improvement on these coatings is the deposition of aluminum oxide which frequently serves the purpose. The most practical method of making strips from which these coils are formed is to cut them from a wider aluminum strip which has been coated previously with a dielectric material. The major advantage in coating dielectric material over a single wide strip and subsequently cutting it to individual narrow strips is that the insulated coating can be formed with much more uniform thickness and quality than can many narrower coatings. Also, a succession of individual coatings cannot be applied nearly as economically as can one single coating.

It is evident, however, that when a relatively wide dielectric coated strip is cut longitudinally into narrower strips the cutting operation exposes the aluminum base material at the edge portions of the narrower strips and leaves them rough with slivers and burrs and, of course, uninsulated. These bared edge portions must be insulated or else they will cause short circuits between the turns of the resultant coil. Among the various proposals which have been suggested for insulating the edges in an economical and satisfactory manner and one which has been generally adopted to be the most favorable, is to submit the edges of the strip to an anodizing operation.

The method presently being followed for edge anodizing rolls of strip conductor material has been to make anode contact with the outermost and innermost turns in a roll of conductor material. When such contact is made, the oxidic formation is initiated at the points of anode contact and forms outwardly therefrom. As the edge of one turn of one layer of strip conductor material becomes effectively insulated the electric current must pass through the insulated turn thereafter, and it has been found that as the number of insulated turns increases, the resistance to the flow of electric current through the several turns correspondingly increases, thus causing a serious voltage dnop This voltage drop causes a decrease in the efiiciency of anodizing, thereby resulting in formations of weak oxidic insulation and increased periods for complete anodizing of the edges of the rolls.

I have found that by making anode contact along a portion of the side edges of a plurality of turns in a roll of strip conducter material the electric current flows within each of the turns substantially simultaneously. This substantially unform current flow effectively decreases the anodizing time as well as contributes to the deposition of a superior insulation on the edges. I have found that this improvement can particularly be used in the method of forming electric coils from rolls of strip conductor material which have uninsnlated side edges. The improved steps in the method of anodizing the edges of rolls of strip conductor material are comprised of making anode contact along an edge portion of each turn of a roll of strip conductor material and anodizing the side edges of the strip conductor material while making said anode contact. The resultant edge anodized strip is then wound into a coil such that the contacted edge portions in substantially any turn of the strip of the coil are out of registry with the contacted portions in an adjacent turn of the coil. It is of course contemplated that the novel steps of the method of the invention may be used, wherever practical, in combination with the ordinary steps used in the method of forming electric coils from rolls of conductor material having uninsulated side edges.

The invention also provides a novel anodizing rack for edge anodizing the rolls of strip conductor material according to the method of the invention. Broadly stated, the anodizing rack of the invention is comprised of an anode supporting member on which at least one roll can be mounted and anode contact members which are mounted on the supporting member and extend outwardly therefrom to make anode contact on an edge portion of a multiplicity of turns in said rolls. Locking means can also be provided on the supporting member for maintaining the contact members and rolls on. the supporting member with proper contact therebetween. The anodizing rack of the invention can accommodate a plurality of rolls of conductor material and thus can be used for batch anodizing rolls. Moreover, it is also contemplated that the anodizing rack can be suspended into a bath of electrolyte in a horizontal or vertical direction whichever may be desired.

In a preferred embodiment of the new method, a relatively wide strip of aluminum of a thickness of say .003 inch, is run over one or more applicator rolls carrying a liquid organic dielectric coating composition, whereby a layer of such composition of uniform thickness is transferred to one or both the surfaces of the advancing aluminum strip. Upon emerging from this coating apparatus, the coating composition is dried to a hardened condition. Alternatively, the wide strip may be covered by an inorganic dielectric coating, such as an anodic film, in which case the later-applied anodic edge-coating is still separate from insulation on the broad surface of the strip. The coated wide strip is then directed through continuous cutting apparatus where it is divided longitudinally into a plurality of narrow strips, each the width of a roll. Any type of cutter used in this step bares the aluminum base metal and leaves a certain amount of slivers, burrs, or other irregularities on the edges of the narrow strip.

The narrow strips exiting from the cutting apparatus are then directed into winding apparatus where they are formed into rolls of a multiplicity of turns. The flat sides of the cylindrical rolls so wound are defined, of course, by the exposed edges of the aluminum strip which are in ragged condition as a result of the cutting operation. The rolls are then taken in batches to anodizing equipment which is constructed to make anode contact along an edge portion of a multiplicity of turns in each roll. The rolls thus contacted are subjected to conventional cleaning operations and then are lowered into an electrolytic bath which may advantageously be chromic, sulphuric, oxalic, or other acid, or it may be a caustic alkaline bath. Low voltage direct current (or sometimes alternating current) is passed through the bath with each of the rolls therein serving as the anode. A lead, stainless steel or other conducting electrode is employed as the cathode. The roll being contacted along a multiplicity of turns, caused the current to flow substantially uniformly throughout the turns of the coil with substantially constant resistance and thus little voltage drop between turns in the roll. Hence, the resultant anodic deposit was substantially uniform throughout the edge of the roll.

When the anodizing is completed, the batch of rolls is lifted from the bath, rinsed and dried. The resulting rolls each comprise a multiplicity of turns of aluminum strip which is electrically insulated on one or both faces by the coating composition, and at both side edges by the oxidic anodized film. Of course, where anodic contact was made at a portion of the turns in the roll, no oxidic film has been deposited and it remains uninsulated. By using knife edge contacts however, this can be kept at a minimum since only a minute cross-sectional edge portion of the strip has been contacted. Moreover, in the next step of rewinding the strip from the roll into electrical coils, a novel step in the method of the invention provides winding the coil such that the contacted edge portions in one turn of the strip in the coil are substantially out of registry with the contacted portion in an adjacent turn in the coil.

A preferred embodiment of the anodizing apparatus of the invention is described hereinbelow with reference to the accompanying drawing wherein:

FIG. 1 is an elevation of the horizontally suspended embodiment of the anodizing apparatus of the invention;

FIG. 2 is a side elevation partly in section and partly broken away of the vertically suspended embodiment of the anodizing apparatus of the invention;

FIG. 3 is a section taken substantially along line 3-3 of FIG. 1; and

FIG. 4 is a perspective of an anode contact of the apparatus.

Referring initially to FIG. 1 a tank having a flange portion 11 formed thereon is substantially filled with a bath 12 of electrolyte. Positioned on the flange portion 11 on opposite sides of the tank 10 are suitable mounting members 13 and 14. The mounting members 13 and 14 serve to maintain a suspension bar 15 across the span of the tank 10, thereby overlying the bath 12. The suspension bar 15 has an electrical terminal 16 secured to one portion thereof which is connected by electrical conductors 17 to a suitable D.C. source to deliver a positive electrical charge. Mounted on the suspension bar 15 and depending therefrom to a substantial distance within the tank 10 and submerged in the electrolyte 12 during the anodizing operation are hangers 18 and 19. The hangers 18 and 19 serve to hold a supporting rod 20 at substantially opposite ends thereof and thus maintain the rod in a substantially horizontal position. The rod 20, as best shown in FIG. 2, is threaded along substantially its entire intermediate length 22.

A plurality of rolls 23 of strip conductor material are slidably mounted on the rod 20 along the threaded portion 22 so that they are positioned substantially concentr ically thereon. Positioned axially along the rod 20 and disposed between each of the respective rolls 23 to maintain the rolls in spaced relationship along the axial extent of the rod 20 as well as to make contact along a minute side edge portion of each turn of the rolls 23, are anode contact members 25. As best shown in FIG. 4 the anode contact members 25 are, in this preferred embodiment, comprised of an internal sleeve portion 26 whlch has an inside diameter substantially equal to the outside diameter of the rod 20 and has contact arms 27 which extend radially outward from the sleeve member '26. The contact arms 27 are of very small knife-like thickness at least along that edge portion thereof which is adapted to abut the flat edges of the rolls 23. Thus, only a minute cross section of the flat edge of each turn is contacted by the arms 27. Although not shown, it has been found that the contact members 25 are not required to have the arms 27 thereof extending radially outward in the same direction, rather the arms of each of the members can extend in different directions than the arms of other members and nevertheless function properly.

After the rolls 23 and contact members 25 are alternately mounted on the rod 20, a pressure plate 28 is brought flush against the last contact member to be loaded thereon and is longitudinally compressed by means of a lock nut 29 which is threaded onto the threaded length 22 of the rod 20. By this means the entire assembly can be maintained tightly compressed together with the anode contact members 25 abutting fiushly against the fiat side edges 30 of the rolls 23.

In both embodiments shown in the drawing a permanent contact member 31 forms an integral part of the rod 20. The permanent contact member 31 is mounted on one end portion of the rod 20 opposite to the end portion of the rod in which the lock nut 29 is threaded, and thus opposite to the end of the rod on which the rolls 23 and contact member 25 are loaded thereon. By providing a permanent contact member 31, it serves in both instances as a base member against which the plurality of rolls 23 and spacers 25 can be compressed axially along the rod 20 so as to maintain these elements in tight compression. As shown, contact arms 32 of the permanent contact 31 converge to a knife-edge 33 from a substantially wide base 34, thereby providing the smallest area of contact with sufficient structural support.

In FIG. 2 a vertical support assembly is shown. The vertical support assembly is comprised of the same elements described above in relation to the horizontal assembly, the disposition of the assembly being vertically suspended into the bath 12 of electrolyte by means of a hanger 35 which is suitably mounted on the suspension bar 15 and attached to one end of the rod 20.

Of the two embodiments the horizontal anodizing rack assembly is the most desirable. Owing to the weight of the plurality of rolls 23 and contact members 25 is it possible that the knife-edged arms 27 of the contact members could score the fiat edges of the rolls 23 and mechanically distort these edges. Moreover, it is possible that some electrolyte may be drawn between the respective turns of the rolls 23 by capillary action and this is also undesirable. All of these difiiculties are obviated with the horizontal anodizing assembly.

I claim:

1. In a method of forming electrical coils from rolls of strip conductor material having uninsulated side edges which have a metal surface capable of being anodized, the improvement comprising:

(a) making knife-edged anode contact along a portion of the side edges of a plurality of turns in a roll of strip conductor material,

v(b) anodizing the side edges of the strip conductor material while making said anode contact, and

(c) unwinding the roll and winding the resultant edge anodized strip into a coil with insulation between the turns of the coil and having a different number of turns than the roll such that said uninsulated contacted edge portions in substantially any turn of the strip in the coil are out of registry with the contacted portions in an adjacent turn in the coil.

2. In a method of forming electrical coils from rolls of aluminum strip conductor material having uninsulated side edges which have a metal surface capable of being anodized, the improvement comprising:

(a) making knife-edged anode contact along a portion of the side edges of a plurality of turns in a roll of aluminum strip conductor material,

(b) anodizing the side edges of the aluminum strip conductor material while making said anode contact, and

(c) unwinding the roll and winding the resultant edge anodized strip into a coil with insulation between the turns of the coil and having a different number of turns than the roll such that said uninsulated contacted edge portions in substantially any turn of the strip in the coil are out of registry with the contacted portions in an adjacent turn in the coil.

3. In a method of forming electrical coils from rolls of strip conductor material having uninsulated side edges which have a metal surface capable of being anodized, the improvement comprising:

(a) making knife-edged anode contact along at least one minute edge portion of each turn of a plurality of rolls of strip conductor material,

(b) anodizing the side edges of the strip conductor material of each roll while making said anode contact, and

(c) unwinding the roll and winding each resultant edge anodized strip into a coil with insulation between the turns of the coil and having a difierent number of turns than the roll such that said uninsulated contacted edge portions in one turn of the strip in the coil are substantially out of registry with the contacted portions in an adjacent turn in the coil.

References Cited UNITED STATES PATENTS 12/1951 Gier et a1. "29-15557 2/ 1954 Robinson. 8/1956 Shepard et al. 204-297 XR 8/1958 Roach 29-15562 XR 8/1961 Ramirez et al. 204-58 XR 8/ 1961 Worcester 336-232 XR 5/1962 Rosner 204297 11/1962 Cammauf 29-155.57 4/1964 Manning et al. 29527 12/1965 Smith 317158 FOREIGN PATENTS 7/ 1937 England.

JOHN F. CAMPBELL, Primary Examiner. J. H. MACK, R. W. CHURCH, Assistant Examiners. 

1. IN A METHOD OF FORMING ELECTRICAL COILS FROM ROLLS OF STRIP CONDUCTOR MATERIAL HAVING UNINSULATED SIDE EDGES WHICH HAVE A METAL SURFACE CAPABLE OF BEING ANODIZED, THE IMPROVEMENT COMPRISING: (A) MAKING KNIFE-EDGED ANODE CONTACT ALONG A PORTION OF THE SIDE EDGES OF A PLURALITY OF TURNS IN A ROLL OF STRIP CONDUCTOR MATERIAL, (B) ANODIZING THE SIDE EDGES OF THE STRIP CONDUCTOR MATERIAL WHILE MAKING SAID ANODE CONTACT, AND (C) UNWINDING THE ROLL AND WINDING THE RESULTANT EDGE ANODIZED STRIP INTO A COIL WITH INSULATION BETWEEN THE TURNS OF THE COIL AND HAVING A DIFFERENT NUMBER OF TURNS THAN THE ROLL SUCH THAT SAID UNINSULATED CONTACTED EDGE PORTIONS IN SUBSTANTIALLY ANY TURN OF THE STRIP IN THE COIL ARE OUT OF REGISTRY WITH THE CONTACTED PORTIONS IN AN ADJACENT TURN IN THE COIL. 